Establishment Of Highly Efficient In Vitro Regeneration System And Induction Of Resistance In Strawberry ’jingyao’

Strawberry (Fragaria ananassa Duch.), which belongs to the Fragaria genus, Rosaccae Family, is one of the most important commercial fruit crops in the world. Strawberry cultivars are highly heterozygos and the hybrid progenies are widely separated, which makes it much more difficult for cross breeding. Moreover, the conventional breeding techniques are laborious, costly, time-consmuing and low efficient to improve strawberry quality and yield. Recent advances and applications in genetic engineering technology provide a new path for strawberry molecular breeding. Chemical fungicides which are generally applied as a traditional method to control strawberry diseases are followed by problems like fungicide residues and the environment pollution. By using some external factors to induce plant resistance plants can resist disease through their own defence system. This biological measure avoids a series of problems such as chemical pesticide residue and is gradually applying to prevent and control on crops diseases.An efficient tissue culture system is thought to be crucial to the success of plant genetic engineering. In this research, we have studied the effects of a series of cultural factors (basic media, plant growth regulator, dark incubation, AgNO3concentration, inoculation methods, different location of leaves and leaf ages) in the inducing adventitious shoot of strawberry, respectively. Therefore, an efficient regeneration system of strawberry cultivar’JingYao’was established. In addition, preliminarily studies were done to induc resistance of strawberry by cultures of Colletotrichum from strawberry. And changes of SOD, POD and CAT activities in strawberry leaves were measured after different treatments. The major results can be summarized as below:1. The regeneration system of’JingYao’has been established.(1) To compare the effects of the basic media, MS, MS minerals plus B5vitamins and B5, on the adventitious shoot regeneration from the leaves of strawberry’JingYao’, it was found that MS produced the highest shoot regeneration rate, which was significantly different from that of MS minerals plus B5vitamins and B5(2). To compare the effects of different combinations of plant growth regulators on the rate of adventitious shoot regeneration and their quality, it was found that the optimal initiation medium for adventitious shoot regeneration of leaves and petiole was respectively as follows:For leaves of’JingYao", adventitious shoot regenerated best on MS supplemented with2.0mg/L TDZ and0.05mg/L2.4-D with regeneration rate of79.17%; For petiole of ’JingYao’, adventitious shoot regenerated best on MS supplemented with3.0mg/L TDZ and0.05mg/L2,4-D with regeneration rate of41.67%.(3) For’JingYao’, one week of dark treatment increased the rate of adventitious shoot regeneration from60.8%to85.8%. However, the adventitious shoot regeneration rate decreased with the extension of dark periods.(4) The rate of adventitious shoot regeneration was significantly decreased with different concentrations of AgNO3added into the medium. And the higher concentration of AgNO3was, the more obvious inhibition was observed.(5) The different location of leaves played a role in the adventitious shoot regeneration of ’JingYao’. The rate of adventitious shoot regeneration with the base of leaves as explants was much higher than that with the apical of leaves as explants, but when compared with the central of leaves, there was no evident difference. There was not any notable difference on the regeneration rate of adventitious shoot whether leaf discs were placed abaxial side up or down. But the latter was better. The rate of adventitious shoot regeneration with the second and third leaves as explants was much higher than that with the first, fourth and fifth leaves as explants.2.The results showed that the cultures of Colletotrichum fragariae Brooks from strawberry could induce the resistance on ’JingYao’ to strawberry anthracnose.(1) The leaves of ’JingYao’ were spied by the filter-sterilized mycelium, which came from the fermentation products of strawberry anthracnose. Three days later, strawberry anthracnose was inoculated. The results showed that the resistance of ’JingYao’ was enhanced. Disease incidence was lower compared with control. It was supposed that the filter-sterilized mycelium could induce the resistance on ’JingYao’ to strawberry anthracnose.(2) The changes of SOD, POD and CAT activities were measured after different treatments on strawberry leaves. Results showed that the activities of SOD, POD and CAT contained in ’JingYao’ leaves could be enhanced after treatment with the filter-sterilized mycelium. It was supposed that the development of induced resistance in ’JingYao’ leaves was most likely to be associated with the changed activities of these defense enzymes.